A conventional gas turbine includes a rotor with various rotor blades mounted to rotor disks in the fan, compressor, and turbine sections thereof. Each blade includes an airfoil over which the pressurized air flows, and a platform at the root of the airfoil that defines the radially inner boundary for the airflow. The blades are typically removable, and therefore include a suitable dovetail configured to engage a complementary dovetail slot in the perimeter of the rotor disk. The dovetails may either be axial-entry dovetails or circumferential-entry dovetails that engage corresponding axial or circumferential slots formed in the disk perimeter. A typical dovetail includes a neck of minimum cross sectional area extending radially inwardly from the bottom of the blade platform. The neck diverges outwardly into a pair of opposite dovetail lobes.
For circumferential dovetails, a single dovetail slot is formed between forward and aft continuous circumferential posts or “hoops” and extends circumferentially around the entire perimeter of the disk. An example of this type of configuration is shown in U.S. Pat. No. 6,033,185. The circumferential slot may be locally enlarged at one location for allowing the individual dovetails to be initially inserted therein and then repositioned circumferentially along the dovetail slot until the entire slot is filled with a full row of the blades. The cross-sectional shape of the circumferential dovetail slot includes lobe recesses defined by forward and aft rotor disk hoops that cooperate with the dovetail lobes to radially retain the individual blades against centrifugal force during turbine operation.
A plurality of blades, specifically the dovetail component, are slid into and around the circumferential slot to define a complete stage of rotor blades around the circumference of the rotor disks. The blades include platforms at the root end that may be in abutting engagement around the slot. In other embodiments, spacers may be installed in the circumferential slot between adjacent rotor blade platforms. Once all of the blades (and spacers) have been installed, a final remaining space in the slot is typically filled with a specifically designed spacer assembly, as generally known in the art.
Various conventional spacer assemblies are relatively complicated multi-component devices that rely on a bolt, cam, or other torque mechanism that is turned to actuate oppositely disposed move members into engagement with the disk hoops. The cam piece, bolt, or other functional member is then locked down. Other devices radially bolt the two pressure faces together. These conventional systems are generally difficult to assemble, and are prone to coming apart during operation of the turbine, for example if either side of the devices develop clearance relative to adjacent turbine components (i.e., the rotor disks or blade platforms). Another problem often encountered in conventional designs is that the components are difficult to fit together.